Option (b).

The author says “richer areas have more sex selection than poorer ones and sex selection tends to rise as countries get richer”. He then gives the example of Shanghai and Tibet in support of his stand. Hence option (b).

 Option A

“How do clear, and thus nutrient-poor, waters support such prolific and productive communities?” This is the first question that arises in the author’s mind when he thinks about the corals. On his intent to find out the answer, he discovered that the corals produce food for themselves through the zooxanthellae algae using the metabolic wastes of themselves and hence they actually thrive in water that are relatively low in nutrients. He also explains that human activities increase nutrient content in these waters and degradation of shallow waters and hence cause deterioration of coral reefs. So we can conclude that coral reef communities may actually be more likely to thrive in waters that are relatively low in nutrients.

The correct answer is D. The paragraph is a listing of various types of clocks and how they work.

 Option D

The author says that human activities such as agriculture, slash-and-burn land clearing, sewage disposal and manufacturing create waste by-products and increase nutrient loads in these waters thereby threatening reef communities sensitive to subtle changes in nutrient input to their waters. Option (D) is the obvious choice

 The correct answer is C.

I) Incorrect-the author says “The clock is a very old invention,” he does not state that the clock is people’s oldest invention.

II) Incorrect. While the para states that “Sundials were used in ancient times,” there is no mention of whether it was the oldest type of clock.

III) Correct. The author states that “Mechanical clocks appeared in the 13th century in Europe. They work with a system of moving gears.”

The correct answer is C.The passage states that “Auditory clocks use language to tell the time aloud,”and hearing the sense which would be associated with time told aloud, it is very likely that the word auditory is related to hearing.We can easily eliminate all the other options

 Option B

“Unfortunately for coral reefs, however, a variety of human activities are causing worldwide degradation of shallow marine habitats by adding nutrients to the water….” The author’s views are clear in the above lines where he tries to cite out the human activities which have resulted to be a threat for the corals as slash-and-burn land clearing and sewage disposal. Although the author mentions how coral reefs produce food for themselves, that is not the central idea and hence option D is wrong. The author does not discuss deterioration about algae, option A is eliminated. Coral reefs do not deteriorate in nutrient poor waters. Option C is incorrect.